This section is intended to provide a background or context. The description herein may include concepts that could be pursued, but are not necessarily ones that have been previously conceived, implemented or described. Therefore, unless otherwise indicated herein, what is described in this section is not prior art to the description and claims in this application and is not admitted to be prior art by inclusion in this section.
The following abbreviations that may be found in the specification and/or the drawing figures are defined as follows:
3GPP third generation partnership project
ACK acknowledge
BS base station
CQI channel quality indicator
DL downlink (eNB towards UE)
eNB E-UTRAN Node B (evolved Node B)
EPC evolved packet core
E-UTRAN evolved UTRAN (LTE)
FDMA frequency division multiple access
HARQ hybrid automatic repeat request
HSDPA high speed downlink packet access
HSPA high speed packet access
IMTA international mobile telecommunications association
ITU-R international telecommunication union-radiocommunication sector
LTE long term evolution of UTRAN (E-UTRAN)
LTE-A LTE advanced
MAC medium access control (layer 2, L2)
MIMO multiple input multiple output
MM/MME mobility management/mobility management entity
NACK negative acknowledge
NodeB base station
O&M operations and maintenance
OFDMA orthogonal frequency division multiple access
PCI precoding control indicator
PDCP packet data convergence protocol
PHY physical (layer 1, L1)
PUCCH physical uplink control channel
PUSCH physical uplink shared channel
RAT radio access technology
Rel release
RLC radio link control
RRC radio resource control
RRM radio resource management
SC-FDMA single carrier, frequency division multiple access
SGW serving gateway
TB transport block
TDM time division multiplex
TTI transmit time interval
UE user equipment, e.g., a mobile station, mobile node or mobile terminal
UL uplink (UE towards eNB)
UPE user plane entity
UTRAN universal terrestrial radio access network
One modern communication system is known as evolved UTRAN (E-UTRAN, also referred to as UTRAN-LTE or as E-UTRA). In this system the DL access technique is OFDMA, and the UL access technique is SC-FDMA.
One specification of interest is 3GPP TS 36.300, V8.11.0 (2009-12), 3rd Generation Partnership Project; Technical Specification Group Radio Access Network; Evolved Universal Terrestrial Radio Access (E-UTRA) and Evolved Universal Terrestrial Access Network (EUTRAN); Overall description; Stage 2 (Release 8), incorporated by reference herein in its entirety. This system may be referred to for convenience as LTE Rel-8. In general, the set of specifications given generally as 3GPP TS 36.xyz (e.g., 36.211, 36.311, 36.312, etc.) may be seen as describing the Release 8 LTE system. More recently, Release 9 and Release 10 versions of at least some of these specifications have been published including 3GPP TS 36.300, V10.2.0 (2010-12).
FIG. 1A reproduces FIG. 4-1 of 3GPP TS 36.300 and shows the overall architecture of the EUTRAN system (Rel-8) 100. The E-UTRAN system 100 includes eNBs 120, 124, 128, providing the E-UTRAN user plane (PDCP/RLC/MAC/PHY) and control plane (RRC) protocol terminations towards the UEs (not shown). The eNBs 120, 124, 128 are interconnected with each other by means of an X2 interface 130. The eNBs 120, 124, 128 are also connected by means of an S1 interface 135 to an EPC, more specifically to a MME by means of a S1 MME interface and to a S-GW by means of a S1 interface (MME/S-GW 110, 115). The S1 interface 135 supports a many-to-many relationship between MMEs/S-GWs/UPEs 110, 115 and eNBs 120, 124, 128.
The eNB hosts the following functions:                functions for RRM: RRC, Radio Admission Control, Connection Mobility Control, Dynamic allocation of resources to UEs in both UL and DL (scheduling);        IP header compression and encryption of the user data stream;        selection of a MME at UE attachment;        routing of User Plane data towards the EPC (MME/S-GW);        scheduling and transmission of paging messages (originated from the MME);        scheduling and transmission of broadcast information (originated from the MME or O&M); and        a measurement and measurement reporting configuration for mobility and scheduling.        
Of particular interest herein are the further releases of 3GPP LTE (e.g., LTE Rel-10) targeted towards future IMT-A systems, referred to herein for convenience simply as LTE-Advanced (LTE-A). Reference in this regard may be made to 3GPP TR 36.913 V9.0.0 (2009-12) Technical Report 3rd Generation Partnership Project; Technical Specification Group Radio Access Network; Requirements for further advancements for Evolved Universal Terrestrial Radio Access (E-UTRA) (LTE-Advanced) (Release 9). Reference can also be made to 3GPP TR 36.912 V9.3.0 (2010-06) Technical Report 3rd Generation Partnership Project; Technical Specification Group Radio Access Network; Feasibility study for Further Advancements for E-UTRA (LTE-Advanced) (Release 9).
A goal of LTE-A is to provide significantly enhanced services by means of higher data rates and lower latency with reduced cost. LTE-A is directed toward extending and optimizing the 3GPP LTE Rel-8 radio access technologies to provide higher data rates at lower cost. LTE-A will be a more optimized radio system fulfilling the ITU-R requirements for IMT-Advanced while keeping the backward compatibility with LTE Rel-8.
As is specified in 3GPP TR 36.913, LTE-A should operate in spectrum allocations of different sizes, including wider spectrum allocations than those of LTE Rel-8 (e.g., up to 100 MHz) to achieve the peak data rate of 100 Mbit/s for high mobility and 1 Gbit/s for low mobility. It has been agreed that the wider bandwidths for LTE-A are achieved through aggregating up to 5 component carriers, each up to 20 MHz wide to achieve the up to 100 MHz wide spectrum allocation. The carrier aggregation could be contiguous or non-contiguous, that is, the component carriers may be adjacent to each other, or non-adjacent to each other. This technique, as a bandwidth extension, can provide significant gains in terms of peak data rate and cell throughput as compared to non-aggregated operation as in LTE Rel-8 where the maximum operation bandwidth is 20 MHz.
A LTE-A terminal may simultaneously receive one or multiple component carriers depending on its capabilities. A LTE-A terminal with reception capability beyond 20 MHz can simultaneously receive transmissions on multiple component carriers. A LTE Rel-8 terminal can receive transmissions on a single component carrier only, provided that the structure of the component carrier follows the Rel-8 specifications. Moreover, it is required that LTE-A should be backwards compatible with Rel-8 LTE in the sense that a Rel-8 LTE terminal should be operable in the LTE-A system, and that a LTE-A terminal should be operable in a Rel-8 LTE system. This requirement is met by ensuring that at least one LTE-A component carrier follows the Rel-8 LTE specifications.
FIG. 1B shows an example of the carrier aggregation, where M Rel-8 component carriers 210 are combined together to form M times Rel-8 BW (e.g. 5*20 MHz=100 MHz given M=5). Rel-8 terminals receive/transmit on one component carrier 210, whereas LTE-A terminals may receive/transmit on multiple component carriers 210 simultaneously to achieve higher (wider) bandwidths.
FIG. 1C shows another example of the carrier aggregation where two component carriers 222, 224 are adjacent to each other on one frequency band 220, and a third component carrier 235 is on another frequency band 230 non-adjacent to the other two. Both intra-band (Carriers 1 and 2) and inter-band (Carrier 3 combined with Carriers 1 and 2) carrier aggregation are shown.
Similar carrier aggregation work has also been carried out in the 3GPP in the context of HSDPA from Release 8 onwards. Release 8 specified dual-carrier HSDPA supporting aggregation of two 5 MHz HSDPA carriers together, Release 10 specified 4-carrier HSDPA, and in Release 11 the work on 8-carrier HSDPA is currently ongoing with the goal being to provide support for up to eight 5 MHz HSDPA carriers.